A. Technical Field
The present invention relates to a method of processing radioactive liquid wastes containing radioactive ruthenium. More particularly, the invention relates to a method for processing such radioactive liquid wastes by using an adsorbent comprising a mixture of activated carbon with zinc and palladium powders.
B. Prior Art
Radioactive ruthenium (.sup.106 Ru) in radioactive liquid wastes react with nitric acid present in the processing of said wastes to form various nitrosyl compounds. Since these compounds are dissolved in the form of various complex salts, one method is capable of removing only a specific compound, and other nitrosyl compounds are left unremoved.
While many radioactive substances are present in the liquid wastes that are discharged into oceans from spent fuel reprocessing plants after being subjected to a chemical treatment such as concentration by evaporation, settlement by coagulation, or ion exchange reaction, .sup.106 Ru accounts for more than half of such radioactive substances. However, experiments conducted so far have shown that .sup.106 Ru cannot be removed with high efficiency by settlement after coagulation or ion exchange. The technique of concentration by evaporation is more effective than these two methods but its effectiveness is reduced if the radioactive liquid wastes contain a large amount of .sup.106 Ru in an highly volatile chemical form.
Japanese Patent Public Disclosure No. 50698/1982 (Japanese Patent Application No. 126401/1980) shows a method of removing .sup.106 Ru from radioactive liquid wastes by passing it through a column packed with a mixture of metal powder and activated carbon. However, this prior art technique has yet to be improved in respect of its ability to remove .sup.106 Ru.
As will be clear from the above explanation, .sup.106 Ru is one of the nuclides that are most problematic in the processing of radioactive wastes, and the development of a safe and efficient method of removing .sup.106 Ru without causing environmental pollution is greatly needed.